The present invention relates generally to internal combustion engines. More particularly, the present invention concerns internal combustions of the type using a transfer chamber to separate the intake and compression functions from the exhaust and expansion functions.
It has long been known that internal combustion engines generate useful power from a charge of fuel mixed with atmospheric air. Typically, the engine ingests a charge of a fuel-air mixture engine, compresses it to a small fraction of its original volume, ignites the compressed charge with, for example, a spark, allows the combustion products to expand against a piston, and finally exhausts the combustion products. Ordinarily, all of the foregoing steps occur in a single piston cylinder arrangement.
Where a single piston cylinder arrangement is employed, the expansion of the combustion products which occurs during the expansion phase of operation, does not reduce the pressure of the combustion products to ambient pressure, or for that matter, a pressure close to ambient. As a result of this characteristic, energy in the form of elevated pressure and elevated temperature is not recovered prior to rejection of exhaust products to the atmosphere. By failing to harness the available energy, the thermodynamic cycle efficiency of such internal combustion engines is, naturally, lower than it might otherwise be.
When the relatively high pressure combustion products are exhausted to the atmosphere, pressure pulses occur which are the source of acoustic noise. This acoustic noise usually requires a muffler in the exhaust system in order to be environmentally acceptable. However, the presence of a muffler in the exhaust system creates a back-pressure on the internal combustion engine cycle which contributes even further to diminished thermodynamic cycle efficiency.
In the past, various techniques have been considered to overcome the deficiencies of the conventional internal combustion engine cycle described above. In one such device, a piston cylinder assembly has been provided which has an annular expansion-exhaust chamber surrounding a central cylindrical intake-compression chamber with a piston arrangement that reciprocates in both chambers simultaneously. See, U.S. Pat. No. 4,096,835 issued June 27, 1978 to Charles E. Lamont. This device uses a valving arrangement to control the transfer of compressed gases from the central chamber to the annular chamber disposed circumferentially with respect thereto. Difficulty in aspirating the central cylindrical intake-compression chamber coupled with substantial heat loss associated with the very high surface to volume ratio in the combustion chamber lead to practical problems in this device.
Other devices have also been proposed in which the compression and expansion functions are separated. To effect this separation, a rotating valve assembly having an internal transfer chamber has been employed. See, for example, U.S. Pat. No. 3,555,814 issued Jan. 19, 1971 to Morsell, III. Such devices are, however, not satisfactory since the combustion chamber is contained in the rod itself. With the combustion chamber in the rod, the hot, high pressure combustion products cause extremely high thermal stresses in the valve rod and result in a risk of explosion. In an analogous device, sliding valves are provided in a conduit which valves effect the transfer of the gaseous charge from a separate compression cylinder to a distinct expansion cylinder. See, for example, U.S. Pat. No. 611,125 issued Sept. 20, 1898 to Humphrey.
Another device, attributed to Kristiansen, sought to provide increased expansion when compared to the compression ratio by using a cylinder type engine in which the cylinders rotated about a drum cam. The cam provided considerably increased expansion on the expansion portion of the cycle in comparison to the compression attained in the compression portion thereof. The Kristiansen engine, however, does not have the features making it susceptible to commercialization.
From the foregoing discussion, it will be apparent that the need continues to exist for an internal combustion engine which overcomes problems of the type discussed above while permitting an increased thermodynamic cycle efficiency to be obtained. The increased cycle efficiency is highly desirable in light of the expense of obtaining petroleum and the increased emphasis on efficient utilization of that natural resource.